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| United States Patent |
5,624,570
|
|
Hassick
|
April 29, 1997
|
Method for reducing turbidity in laundry waste water
Abstract
A method for reducing turbidity in laundry waste water comprising the steps
of treating said water with effective amounts of a first polymer comprised
of dimethyl dialkyl ammonium chloride (DMDAAC) and dialkyl diallyl
ammonium monomers (DADAAX) other than DMDAAC having alkyl groups with from
8 to 18 carbon atoms and counterions with an ionization constant greater
than 10.sup.-8, and a second cationic, nonionic or anionic acrylamide
polymer is disclosed.
| Inventors:
|
Hassick; Denis E. (Monroeville, PA)
|
| Assignee:
|
Calgon Corporation (Pittsburgh, PA)
|
| Appl. No.:
|
609707 |
| Filed:
|
March 1, 1996 |
| Current U.S. Class: |
210/728; 210/734; 210/735 |
| Intern'l Class: |
C02F 001/56 |
| Field of Search: |
210/734,735,728
|
References Cited
U.S. Patent Documents
| 3686151 | Aug., 1972 | Keim | 210/734.
|
| 3719748 | Mar., 1973 | Manfroy et al. | 210/734.
|
| 3968037 | Jul., 1976 | Morgan et al. | 210/735.
|
| 4053512 | Oct., 1977 | Panzer et al. | 210/735.
|
| 4108768 | Aug., 1978 | Sebelik et al.
| |
| 4198294 | Apr., 1980 | Deane.
| |
| 4673511 | Jun., 1987 | Richardson et al. | 210/735.
|
| 5013456 | May., 1991 | St. John et al. | 210/735.
|
| 5076937 | Dec., 1991 | Montgomery.
| |
| 5209854 | May., 1993 | Reed et al. | 210/734.
|
| Foreign Patent Documents |
| 2124301 | May., 1994 | CA.
| |
Primary Examiner: McCarthy; Neil
Attorney, Agent or Firm: Mitchell; W. C., Meyers; D. R.
Claims
What is claimed is:
1. A method for reducing turbidity in laundry waste water comprising
treating said water with an effective amount of:
a) a first polymer; and
b) a second cationic, nonionic or anionic acrylamide polymer, wherein
component a) comprises i) about 90 to about 99.9%, by weight, of dimethyl
diallyl ammonium chloride (DMDAAC) and ii) about 0.1 to about 10%, by
weight, of one or more members selected from the group consisting of
dialkyl diallyl ammonium monomers (DADAAX) other than DMDAAC, and wherein
the molecular weight of component a) ranges from about 5,000 to about
3,000,000 and the molecular weight of component b) ranges from about
1,000,000 to about 15,000,000 as determined by Gel Permeation
Chromatography or intrinsic viscosity methods.
2. The method of claim 1 wherein the member selected from the group
consisting of dialkyl diallyl ammonium monomers have the following
structure:
##STR2##
wherein R is C.sub.8 H.sub.17 to C.sub.18 H.sub.37 and X is the monovalent
conjugate base of an acid with an ionization constant of >10.sup.-8.
3. The method of claim 2 wherein X is selected from the group consisting of
fluoride, bromide, chloride, hydroxide, nitrate, acetate, hydrogen
sulfate, dihydrogen phosphates and methosulfate.
4. The method of claim 2 wherein R is C.sub.12 H.sub.25 and X is chloride.
5. The method of claim 1 wherein the ratio in component a) of DMDAAC to
DADAAX is about 95-99.9% to about 0.1-5%, based on total copolymer weight.
6. The method of claim 1 wherein component b) is a high molecular weight
acrylamide copolymer.
7. The method of claim 6 wherein the molecular weight of component b) is
between about 2,000,000 and 10,000,000.
8. The method of claim 1 wherein said effective amount of component a) is
from 1 to 1,000 ppm based upon the weight of the water being treated.
9. The method of claim 1 wherein said effective amount of component a) is
from about 10 to about 500 ppm based upon the weight of the water being
treated.
10. The method of claim 1 wherein said effective amount of component b) is
from about 1 to about 1000 ppm based upon the weight of the water being
treated.
11. The method of claim 1 wherein said effective amount of component b) is
from about 10 to about 300 ppm based upon the weight of the water being
treated.
12. The method of claim 1 wherein the molecular weight of component a) is
between about 10,000 and 1,000,000.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods for reducing turbidity and/or
contamination in laundry waste water by treating the water with an
effective amount of a first polymer comprised of dimethyl diallyl ammonium
chloride (DMDAAC) and a dialkyl diallyl ammonium monomer (DADAAX) other
than DMDAAC, and a second copolymer which is either an anionic, nonionic
or cationic acrylamide polymer.
2. Description of the Background Art
The character of waste water generated by an industrial laundry is in large
part a function of the customer group that the laundry serves. This
customer group typically includes a wide variety of industrial and
commercial firms including but not limited to heavy manufacturing
industries, the electroplating and automotive industries, battery
manufacturers, the service industries, newspapers, printers, auto garages,
schools, and commercial and retail businesses. Because of these diverse
customers, a wide variety of contaminants are present in the waste water
of a typical laundry. Representative of the contaminants are oils and
greases, heavy metals such as lead, cadmium or zinc, suspended solids such
as dirt, hydrocarbon solvents, organic materials and others. Waste water
from industrial laundries further includes in its complex mixture the
soaps and surfactants used for cleaning; it also generally has high
Biological Oxygen Demand (BOD), high Chemical Oxygen Demand (COD) and an
alkaline pH. The range of constituents, as well as the variability that
exists in laundry wastes, makes it a unique waste water to treat. Laundry
waste water is also unique in that most contaminants enter the waste water
not as a result of intrinsic processes or raw materials, but rather as
residual materials discharged from the garments, shop towels, and other
dust control items used by the laundries' customers.
Discharge of this laundry waste water to a municipal Publicly Owned
Treatment Works (POTW) presents a significant problem to commercial
laundries that generate large volumes of waste water containing the types
of contaminants listed above. A typical industrial laundry has 20,000 to
200,000 gallons per day of discharge water. This can typically represent
about 0.2% of the hydraulic load on a municipal treatment plant, yet at
the same time represent 15 to 20% of its treatment load. In order to
comply with local and federal discharge requirements, it is therefore
often necessary to treat laundry waste water prior to discharge of the
water to POTW. Typically, such waste is treated by adding effective
amounts of chemical coagulation and/or flocculation agents, which causes a
major part of the colloidally dispersed solids and oils in the water to be
transformed together with the coagulants and/or flocculants into an easily
separable form, mostly into a non-slimy flocculant deposit. Dissolved air
floatation (DAF) is then typically used to separate the flocculant solids
from the water phase. Vacuum filtration, pressure filtration or belt press
filtration can be used to further dewater the floated solids.
The response of an individual waste water to a polymeric treatment additive
is a complex function of the water's physical and chemical composition
including, for example, the chemical composition of dispersed solid
phases, the types of oils and greases, the average particle size, the size
distribution of all dispersed phases, the washing chemicals and their
concentrations, the temperature, the pH, etc. Added to this complexity is
the presence of microorganisms that change the character of the system
with time.
The terms coagulation and flocculation, as used herein, collectively refer
to the separation of suspended solid particles from aqueous systems. This
generally occurs by neutralizing the charge of the particles
(coagulation), followed by agglomeration of the neutralized solids
(flocculation).
Turbidity, as used herein, is defined as the cloudiness or haziness of a
solution caused by finely suspended particles. Turbidity is measured using
nephelometric turbidity units (NTU). As used herein, low turbidity
suspensions are those generally having a low solids concentration (on a
weight basis), i.e., a solids weight percent of 0.1 or less. This
typically corresponds with an approximate turbidity of 50 NTU's or less,
but may vary due to the nature of the solids or dissolved colored matter.
High solids suspensions include those systems containing in excess of 0.1
weight percent suspended solids, which generally corresponds to a
turbidity of greater than 50 NTU's. The present invention, while useful in
water of any turbidity, is particularly directed to waters having a high
turbidity.
From an ecological and economic viewpoint, the treatment of laundry waste
water represents a problem of constantly increasing importance and
numerous methods of treating this waste water are reported. For example,
U.S. Pat. No. 5,076,937 describes a method for removing impurities such as
the oil and grease associated with a pH activated surfactant from waste
water by deactivating the surfactant to cause release of these impurities,
infusing a gas into the solution, coalescing the oil and grease droplets
with the gas to achieve droplet buoyancy, forming a layer of said droplets
atop said solution, removing said layer and adjusting the pH of the
solution to about neutral.
U.S. Pat. No. 4,198,294 discloses a method of reclaiming waste water by
emulsifying the water with a high molecular weight anionic surface active
oil, breaking the emulsion thereby producing a coherent flocculant which
occludes the insoluble matter suspended in the water, and separating the
flocculant from the purified water.
U.S. Pat. No. 4,108,768 discloses a method of purifying industrial waste
waters by adjusting the pH of the water to at least 11.6, adding calcium
chloride to flocculate oil or grease in the water, adding a coagulant to
agglomerate the flocculant, and removing the flocculant.
Canadian patent 2124301 discloses a demulsifier comprising a hydrophobic
polyelectrolyte copolymer comprising DMDAAC and a hydrophobic monomer. The
hydrophobic monomer disclosed in this patent is selected from a group
consisting of a quaternized dialkylaminoalkyl methacrylates and alkyl
esters of (meth)acrylic acids, and not DADAAX as taught by the present
invention. Moreover, while the patent is directed to waste water in
general it does not specifically delineate efficacy in laundry waste
water.
None of these methods for laundry waste water purification suggests the
methods of the present invention, however.
Other treatments of laundry waste water include treating the water with a
cationic polymer such as poly dimethyl diallyl ammonium chloride (poly
DMDAAC), to destabilize the colloidal solids, followed by addition of a
high molecular weight anionic or cationic acrylamide copolymer. The
inventors have discovered that using a cationic copolymer of DMDAAC and
another DADAAX followed by the addition of a high molecular weight anionic
or cationic acrylamide copolymer results in an unexpected reduction of
turbidity and contamination in the final settled water.
Because of the importance of reducing contamination in laundry waste water
prior to discharge, there remains a very real and substantial need for
improved methods of treating laundry waste water.
SUMMARY OF THE INVENTION
The present invention generally meets the above need by providing a method
for reducing turbidity and/or contamination in laundry waste water
comprising the steps of treating said water with an effective amount of:
a) a first polymer; and b) a second cationic, nonionic or anionic
acrylamide polymer, wherein component a) is prepared using i) dimethyl
diallyl ammonium chloride (DMDAAC) and ii) a dialkyl diallyl ammonium
monomer (DADAAX) other than DMDAAC and component b) is a high molecular
weight cationic, nonionic or anionic acrylamide copolymer.
The polymers used in the methods of the present invention improve
separation performance and thereby allow the operator of an industrial
laundry increased flexibility in operation. These methods achieve improved
discharge limits while using less of the expensive cationic polymers
currently in use.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a method for reducing turbidity in
laundry waste water comprising treating said water with an effective
amount of: a) a first polymer; and b) a second cationic, nonionic or
anionic acrylamide polymer, wherein component a) comprises i) about 90 to
about 99.9%, by weight, of dimethyl diallyl ammonium chloride (DMDAAC) and
ii) about 0.1 to about 10%, by weight, of one or more members selected
from the group consisting of dialkyl diallyl ammonium monomers (DADAAX)
other than DMDAAC and wherein the molecular weight of component a) ranges
from about 50,000 to about 3,000,000 and the molecular weight of component
b) ranges from about 1,000,000 to about 15,000,000 as determined by Gel
Permeation Chromatography or intrinsic viscosity methods. Such methods of
molecular weight determination will be familiar to those skilled in the
art.
More specifically, the DADAAX of component a) is a quaternary dialkyl
diallyl ammonium monomer wherein the alkyl group is selected from alkyl
groups having from about 8 to 18 carbon atoms and wherein said quaternary
dialkyl diallyl ammonium monomer's counterion is selected from the group
consisting of conjugate bases of acids having an ionization constant
greater than 10.sup.-8. Preferably, the alkyl group contains primarily 12
carbon atoms, and the counterion is selected from the group consisting of
fluoride, bromide, chloride, hydroxide, nitrate, acetate, hydrogen
sulfate, dihydrogen phosphates and methosulfate. More preferably, the
counterion is chloride. The monomer is represented by the structure:
##STR1##
where R is C.sub.8 H.sub.17 to C.sub.18 H.sub.37 and X is the monovalent
conjugate base of an acid with an ionization constant of >10.sup.-8.
The diallyl dialkyl ammonium monomers (DADAAX) used in this invention are
conveniently prepared by the reaction of two moles of allyl chloride with
one mole of an alkyl amine followed by reaction with, for example, methyl
chloride or dimethyl sulfate to form the quaternary salt. The long chain
alkyl amines of the DADAAX moiety are usually derived from natural
sources. Accordingly, the alkyl groups may not all contain the same number
of carbon atoms, but rather may contain a mixture of similar chain length
compounds. Typically, however, one chain length will be predominant in the
mixture. Depending on the degree of purification, the alkyl amine will
contain a distribution of carbon chain lengths reflecting the distribution
of the fatty acid from which it is derived. The DADAAX monomer prepared
from the commercial fatty amines, therefore, will not be a pure compound,
but will reflect the same distribution of fatty alkyl chain lengths as the
original fatty amine starting material. This concept is further explained
in the Encyclopedia of Chemical Technology, 4.sup.th Ed., Vol.2, p
405-425.
The quaternary DMDAAC monomer of component a) comprises from about 90 to
about 99.9%, based on total copolymer weight, while the other DADAAX
monomer of component a) comprises from about. 1 to about 10%, based on
total copolymer weight. More preferably, the DMDAAC:DADAAX weight ratio is
from about 99.9:.1 to about 95:5, based on the total weight of the
polymer. Thus, in the component a) copolymers of the present invention,
the DMDAAC moiety of the copolymer is predominant. Additionally, other
moieties may be present in the polymer.
As will be appreciated by one skilled in the art, the first cationic
copolymer used in the present invention, component a), is a hydrophobic
copolymer. Because it is hydrophobic, it is believed to work by combining
with the solids contained in the laundry waste water, though the inventors
do no intend to be bound by any mechanism.
An especially suitable polymer is that in which the DADAAX portion has 12
carbon atoms and the counterion is chloride. Preferably, the DMDAAC:DADAAC
(where C=chloride) weight ratio ranges from about 99.9:0.1 to about 90:10,
most preferably from about 99.9:.1 to 95:5, based on total copolymer
weight.
The component a) copolymers used in the methods of the present invention
may have any molecular weight ranging from about 5,000 to about 3,000,000
with the preferred molecular weight ranging from about 10,000 to
1,000,000. These polymers may be prepared using conventional free radical
polymerization techniques familiar to those skilled in the art.
Component a) as described above functions to coagulate any suspended solids
and emulsified oils which may be present in the laundry waste water. It is
further believed that this coagulation takes place through charge
neutralization of the solids though the inventors do not intend to be
bound by any mechanism. It is well known in the art to use one or more
flocculants to treat coagulated solids to provide better solids removal.
Treatment of the laundry waste water with component a) is therefore
followed by treatment with component b), which serves to agglomerate the
coagulated solids. A variety of conventional polymeric flocculants can be
employed depending on the laundry waste water being treated. It is
preferred that the flocculant used in the methods of the present
invention, referred to as component b) above, be an anionic, nonionic or
cationic high molecular weight acrylamide polymer. The molecular weight
range of component b) is typically between about 1,000,000 and 15,000,000,
more preferably between about 2,000,000 and 10,000,000. Such products are
commercially available from Calgon Corporation, Nalco, and Cytec.
Preferred anionic acrylamides are prepared using (meth)acrylic acid and
acrylamide. Hydrolyzed polyacrylamides can also be used. Generally, the
carboxylic content of the anionic polymers varies from about 10 to 50%, by
weight. Preferred cationic polymers are prepared by the polymerization of
conventional cationic monomers with acrylamide. The cationic moieties
generally comprise up to about 60-70%, based on total polymer weight of
such polymers.
After addition of component b), the agglomeration which forms is removed by
dissolved air flotation or other means typically used in the art.
Coagulation, flocculation and removal of the solids in the laundry waste
water results in a reduction in the turbidity and contamination of the
water being treated.
As stated above, an effective amount of each component must be added to the
laundry waste water being treated. As used herein, the term "effective
amount" refers to that amount of each component necessary to achieve the
desired reduction in turbidity and/or contamination in the waste water
being treated. An effective amount of component a) will typically range
from about 1 to about 1,000 parts per million (ppm) based upon the weight
of the water being treated, with 10 to 500 ppm being the preferred
treatment range. The exact amount of component a) added will depend on how
contaminated the water is; the dirtier the water the more of the polymer
required to coagulate the solids. An effective amount of component b) will
range from about 1 to about 1000 ppm, preferably about 10 to about 300
ppm, based upon the weight of the water being treated. Again, the amount
of component b) used will depend on how much solid is in the water. The
effective amount of component b) will typically increase or decrease with
the amount of component a) needed. The amount of both components also
depends on the level of reduction of turbidity which is desired. These
determinations are well within the ordinary skill of one practicing in the
art.
As an example of a best mode embodiment of the present invention, component
a), the copolymer coagulant, will preferably be a solution polymer in
viscous liquid form. Such solution polymers typically are diluted to about
10% or less upon addition to the laundry waste water being treated,
although higher dilutions are within the scope of the invention. An
effective amount of the final polymer solution is added. Other products
can also be used. The product form selected is a matter of choice
depending upon storage and handling considerations and is not believed to
effect the performance of the polymer. Addition of component a) to the
waste water is preferably at a rapid mix zone, just after equalization.
Thorough mixing of component a) with the waste water is believed to be
important to ensure adequate reaction between component a) and the waste.
Component b), the acrylamide based flocculant, is preferably supplied as an
emulsion product, although dry products can also be used in the methods of
the present invention. The emulsion will typically be used at a working
concentration of about 0.5 to about 2.0% active and added at the influent
to the DAF unit. As will be appreciated by one skilled in the art, too
much agitation or shear may cause the flocculants to break apart thereby
making separation more difficult. The optimal addition points for
components a) and b) are based on the design of the individual laundry,
and is within the skill of one practicing in the art to determine.
EXAMPLES
The following examples are provided to illustrate the invention in greater
detail and should not be construed as limiting the invention in any way.
In Examples I-IV, jar tests were run on water samples taken from industrial
laundries located in Ohio, Massachusetts and Pennsylvania, as indicated
below. The jar tests, which will be familiar to one skilled in the art,
were run according to H. E. Hudson and E. G. Wagner, Conduct and Use of
Jar Tests, JAWWA, Vol. 73, No. 4., p. 218 (1981 ), with the following
particulars:
2 minutes at the maximum RPM following addition of the first cationic
polymer
3 minutes at 70 RPM following addition of the second anionic polymer
5 minutes at 0 RPM.
After the 5 minute settling period, 20 ml samples of supernatant were drawn
and turbidity was measured using a Spectronic 21 DUV set at 450 microns
and using deionized water as the 100% blank.
The following polymer compositions were used in the examples:
PDMDAAC--Commercially available poly dimethyl diallyl ammonium chloride
compounds of varying molecular weight (MW).
81 A--A copolymer of dimethyl diallyl ammonium chloride and methyl octyl
diallyl ammonium bromide prepared with a monomer molar feed ratio of 95/5.
The copolymer had a reduced viscosity of 0.57 dl/gm. The molecular weight
of 81A is about 10,700.
82B--A copolymer of dimethyl diallyl ammonium chloride and methyl dodecyl
diallyl ammonium bromide prepared with a monomer molar feed ratio of
97.5/2.5. The copolymer had a reduced viscosity of 0.81 dl/gm. The
molecular weight of 82B is about 15,300.
83 A--A copolymer of dimethyl diallyl ammonium chloride and methyl
octadecyl diallyl ammonium bromide prepared with a monomer molar feed
ratio of 97.5/2.5. The copolymer had a reduced viscosity of 0.68 dl/gm.
The molecular weight of 83A is about 12,800.
44A--A copolymer of dimethyl diallyl ammonium chloride and methyl dodecyl
diallyl ammonium chloride prepared with a monomer molar feed ratio of
98.7/1.3. The molecular weight of 44A is about 14,500.
A commercially available anionic polyacrylamide having a molecular weight
of about 2-10 million.
EXAMPLE 1
Three waste water samples were evaluated using the identified polymer
compositions. The Ohio #1 sample was treated with 150 ppm ferric chloride,
150 ppm lime, 100 ppm cationic polymer and 16 ppm of anionic
polyacrylamide. The Ohio #2 sample was treated with 20 ppm cationic
polymer and 10 ppm anionic polyacrylamide. The Massachusetts sample was
treated with 80 ppm cationic polymer and 12 ppm anionic polyacrylamide.
The polyacrylamide used in the Example contained about 30% acrylic acid,
by weight, and 70% acrylamide, by weight. The molecular weight of the
PDMDAAC was 94000. Percent transmittance was then determined; results are
presented in Table 1.
TABLE 1
______________________________________
% Transmittance
Sample Name
Ohio #1 Ohio #2 Mass.
______________________________________
PDMDAAC 42.1 24.6 25.2
81A 64.9 23.1 --
82B 49.9 52 --
83A 62.2 42.1 --
44A 69.8 41.7 44.7
______________________________________
As can be seen, the % transmittance of all the copolymers was better than
that of the PDMDAAC alone, except the 81A product at the Ohio #2 location
which gave comparable results. A higher % transmittance indicates that
more solid was removed from the waste water.
EXAMPLE II
Example II was run with waste water samples from a Pennsylvania laundry
facility. The amount of cationic polymer added to each sample is indicated
in Table 2 below; 30 ppm of anionic polyacrylamide, containing about 40%
acrylic acid, by weight, and about 60% acrylamide by weight, was added to
each sample. The molecular weight of the PDMDAAC was 94000.
TABLE 2
______________________________________
% Transmittance
Sample 100 ppm 120 ppm 140 ppm
______________________________________
PDMDAAC 1.1 35.6 77.1
81A 12.6 28.1 36.9
44A 21.6 59.9 85.6
______________________________________
81A was only more effective than the conventional treatment (PDMDAAC) at
the lowest dosage. 44A, however, was superior at all dosages.
EXAMPLE III
Example III was run with waste water from the Ohio #2 location. All of the
samples were adjusted to a pH of 7.0 with sulfuric acid and treated with
200 ppm of ferric chloride followed by the cationic polymer and 15 ppm of
a 30% acrylic acid/70% acrylamide copolymer. PDMDAAC'S of varying
molecular weight were also tested, as indicated in the table.
TABLE 3
______________________________________
% Transmittance
Sample 40 ppm 60 ppm
______________________________________
PDMDAAC - 35000 MW 24.2 41.8
PDMDAAC - 94000 MW 25 40.2
PDMDAAC - 99000 MW 24.4 41.8
PDMDAAC - 840000 MW 24.1 32.3
81A 9.7 23.9
44A 40.2 54
82B 20.5 47.5
83A 21.8 53
______________________________________
This example suggests for this water sample the 44A, 82B and 83A products
perform best when added at an amount greater than 40 ppm.
EXAMPLE IV
In the following example, the cationic polymer was added first in the
amount indicated in Table 4. Anionic polyacrylamide was added
incrementally, in the amounts indicated in Table 4, to achieve the optimum
result for each cationic dose; the polyacrylamide contained about 40%
acrylic acid, by weight, and about 60% acrylamide, by weight. Waste water
samples from the Pennsylvania location were used.
TABLE 4
__________________________________________________________________________
% Transmittance/Anionic Polymer Dosage (ppm)
Cationic Polymer Dosage
Sample 100 ppm
150 ppm
175 ppm
200 ppm
225 ppm
250 ppm
__________________________________________________________________________
PDMDAAC
0.5/30
8.8/30
15.1/30
43.7/30
65.5/25
74.4/25
35000 MW
PDMDAAC
1.3/20
18.1/20
20.2/20
50/20
68.9/15
76.1/15
94000 MW
PDMDAAC
1.4/25
11.2/25
29.2/25
58.2/25
67.9/20
72.8/20
99000 MW
PDMDAAC
2.1/25
20.1/25
27.6/25
59.3/20
70.9/20
66.2/20
840000 MW
44A 45.3/20
67.3/20
78.1/20
78.8/20
83.8/15
78.4/15
__________________________________________________________________________
The hydrophobically modified copolymer (44A) demonstrated improved
performance across the dosage range compared to the conventional treatment
(PDMDAAC).
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